Place the butter in an 8-in. square microwave-safe dish. Cover and microwave on high until melted, about 30 seconds. Stir in cracker crumbs and sugar; press firmly onto the bottom of the dish. Microwave, uncovered, on high for 1 minute. Cool for 5 minutes. In a small bowl, combine 1 cup coconut, milk and nuts; spoon over the crust. Microwave, uncovered, on high for 1-1/2 minutes or until heated through. In a microwave, melt chips and shortening; stir until smooth. Quickly pour over coconut mixture; spread evenly. Toast remaining coconut if desired; sprinkle over the top. Cool on a wire rack; cut into bars. Yield: 16 servings.